The abundance of the water, not only deeply impressed the Valnerina but characterized also strongly the vegetation of theWaterfall Park with native species of great value. There is a Mediterranean climate with a dry summer season and with an average annual temperature above 0° C. These climatic conditions are mitigated at the bottom of the Nerina Valley that is not only narrow and shady, but also very wet. In this area, in fact, the air saturated by many little water particles created by the aerosol phenomenon. The large body of water, falling down with a great impact on the rocks and on the ground at the bottom of the three drops, breaks into little particles and disperses in the air, creating a vapour effect. This complex microclimatic situation appears with a forest mixed with evergreen sclerophylls and with Mediterranean deciduous plants.
The wooden vegetation which covers the slopes and the rocky walls is composed of oak (Quecus ilex), the black hornbeam (Ostrya carpinifolia) recognizable for its lanceolate leaves with serrated margins, the manna ash (Fraxinus ornus) while between the shrubs we can find the laburnum (Laburnum anagroydes), the mountain sorbs (Sorbus aria) and the butcher’s broom (Ruscus aculeatus).
The half-rocky areas characterized by the calcareous rocks are populated by a thick vegetation formed by heather (Erica multiflora), juniper (Juniperus communis and Juniperus oxicedus) and box-tree(Buxus sempervirens), xerothermic relict of the Tertiary, a species of great naturalistic value not very common in Umbria . The wet and travertine rocks are the ideal habitat for fern, musk and liverwort, plants with a very simple anatomy that need a constant presence of humidity to guarantee their own survival and the reproductive phenomena. Among the most representative types of liverwort is the marcascent (Marchantia Polymorpha) presents in the spaces between the rocks where the water constantly passes through and drips; referring to a fern of great value there is the Cervina tongue (phylitis scolopendrium) and the maidenhair fern (Adiantum capillus-veneris) while the more abundant musk there are the Cratoneuron.
All these species create the most peculiar and suggestive park environment: great and soft rugs of emerald which cover the rock stratum penetrated by water!! Along the edges of the Nera river there is the classical riparian vegetation where the trees on the opposite sides can over to form fresh and shady galleries. The white willow (salix alba), the biggest willow with its long branches and silver leaves, the black alder (alnus glutinosa) and the Lombardy poplar (Populus nigras) are the most widely present riparian species.
In Monte Pennarossa, in front of the Falls there are thick patches of ilex grove mingled with Aleppo pine (Pinus halepensis).